CH682896A5 - offset printing machine with variable format with automatic unloading-loading printing cylinders. - Google Patents

Abstract

An offset printing machine is disclosed wherein printing cylinders used for a new run are carried by a carriage into a vicinity of a printing unit of the machine. The printing unit is provided with two lateral movable arms which automatically and successively transfer every printing cylinder from the printing unit onto the carriage and inversely, the new cylinders from the carriage onto the printing unit.

Description

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Description

The present invention relates to variable format web offset printing.

Fig. 1 of the accompanying drawing shows a simplified diagram of the operation of an offset printing machine comprising

- a cylinder PP carrying a metal plate P on which is engraved the printing plate;

- A cylinder PB carrying a rubber plate called blanket B and intended to transfer in the form of a layer of ink the image of the photograph on a corresponding portion, hereinafter called strip F, of cardboard or the like which scrolls;

- a counter-cylinder CC intended to press the strip F in the direction of the cylinder PB;

- an inking unit E comprising an inkwell with adjustable blades Ei, a bubbling roller E2, distributor rollers E3 and touching rollers E4;

- a wetting unit M (with water or alcohol) comprising a tank Mi, a bubbling roller M2, distributor rollers M3 and touching rollers M4.

To make the most of the production capacity of the offset machine, it is known that the three cylinders PP, PB and CC must all have an identical perimeter which corresponds to the length of the format to be printed.

It should be noted that, in particular in the case of advancing the strip F, each printed format may contain one or more printing patterns, each corresponding to a future package. For example, in the case of large laundry cartons, a print may correspond to a cylinder circumference or a print format (minus the dead zone used for fixing the plates and blankets); on the other hand, in the case of liquid boxes, it will take several printing patterns to go around the cylinder. However, this difference does not come into play at the printing level, but only, thereafter where, in the case of packaging, the format is cut into several parts, called poses, each comprising a single pattern and intended to form a packaging copy. Consequently, for each new working series, where the length of the format is different from the previous one, the three rolls PP, PB and CC must be replaced. Since a printing machine can have up to ten groups of PP, PB and CC cylinders, i.e. one group for each color, it follows that up to 30 cylinders are to be exchanged for each new job. One known way of proceeding is to mount the three cylinders by work and group in a cassette comprising rigid frames, high quality gears, crosspieces, bearings, center-to-center adjustments and the three cylinders PP, PB, PC (to name a few than the essential). It is therefore necessary to change the cassette in each group when the format varies.

The disadvantages are:

- high price at job change;

- consequent time to plan a new job (gear cutting, hardening, grinding);

- high idle time at change of job;

- a lot of money frozen in stocks.

Consequently, the object of the present invention is to minimize the manpower and the time necessary for the unloading-loading of the printing cylinders when changing format in an offset printing machine.

This object is achieved by a machine according to claim 1.

Other characteristics and advantages of the invention will emerge from the embodiment described below with reference to the appended drawing in which:

- fig. 1 shows, as already mentioned above, the operating diagram of an offset machine according to the prior art;

fig. 2 and 3 each represent a schematic side view of a printing unit of an offset machine according to the invention;

- fig. 4 is a schematic side view of an offset machine with four printing groups;

- fig. 5 is a schematic view of a part of an offset printing machine provided with a loading-unloading system of the printing cylinders;

- fig. 6 is a functional diagram representing the successive stages of work of the loader-unloader according to FIG. 5;

- fig. 7 is a simplified view of a loading-unloading carriage for the printing cylinders;

- fig. 8 is a partial top view in section along E-E of FIG. 9 of a printing unit provided with a device for unloading-loading the printing cylinders;

- fig. 9 is a view along C of FIG. 8;

- fig. 10 is a sectional view along A-A of FIG. 8; and

- figs. 11 and 11A to 11D are a sectional view of the mounting of the ends of the printing cylinder in an offset machine.

The offset printing machine shown in fig. 2 therefore includes, similarly to FIG. 1 described above, an upper plate cylinder PP, an intermediate blanket cylinder PB, a lower CC cylinder, an inking unit E with its inkwell Ei and its rollers E2-E4, a wetting unit M with its tank Mi and its rollers M2-M4, a washing module L (not shown in fig. 1) of the cylinder PB.

The machine comprises a fixed lower part or frame Ba and a vertically movable upper part, called the CE inking cassette. At each of their ends, the two cylinders PP and CC are mounted for rotation on the first end of a rocking lever 8, respectively 8 ', the second end of which is mounted for rotation about a horizontal axis 81, 81' with fixed prestressed bearings on the Ba frame. On the other hand, the cylinder PB is mounted fixed at each of its ends on the frame Ba. In this way, it is possible, depending on the angular position of the tilting levers 8, 8 ', to put in the working position PP and CC cylinders of different diameters in relation to the length of the for5

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mat to print. In fig. 2, the cylinders PP, PB and CC shown in solid lines corresponding to the maximum format, and those in broken lines in the minimum format.

The inking unit E and the wetting unit M with their elements E1-E4, respectively M1-M4, are mounted directly on the inking cassette CE. Among the distributor rollers E3 or M3, those shown in thick lines are strolls. All touch rollers E4 or M4 are mounted on tilting levers. From fig. 2, it is also possible to see that, thanks to the vertical mobility of the CE cassette and to the touch rollers E4 or M4 mounted on tilting levers, the inking units E and mooring units M can always, that is to say whatever the size of the PP, PB and CC cylinders within the maximum and minimum formats provided, occupy a position which allows them to fulfill their inking or wetting function. As for the washing module L, it is horizontally removable to be adapted to the format of the PB cylinder.

Fig. 3 shows the instant when the cassette CE is at the maximum high point so that, even in the case of the maximum format of the cylinders PB and PP (here the cylinder CC has no influence), the cylinder PP is completely free from the touch rollers E4 and M4. Given, as will be seen later, that the purpose of this clearance is to make it easier to change the cylinders, it has been found that in the highest position of the CE cassette, a distance of at least 50 cm should be provided between the PP cylinder and the nearest E4 or M4 touch roller.

In fig. 4, four printing groups G1-G4, each of which corresponds to a color of the offset printing, are traversed by the strip F in the right-left direction, it being understood that the other left-right direction can also be provided. The first group Gì is intended to print the back of the F band and the next three groups G2-G4 the front. For this purpose, guide rollers R2 are provided around the first group Gì to conduct the strip F, which arrives from the right, over and behind the group Gì which it then crosses in the left-right direction. so that its front is printed by the cylinder PB. Other guide rollers R3 then deflect the strip F, which leaves: from the first group Gi, by 180 ° downwards, in order to orient it again in the right-left direction so as to bring it through the base of the first group Gì, in the direction of the guide rollers R4 provided on the second group G2. Rollers R4 arranged so as to bring the strip F to the level and in the direction of the cylinder PB of group G2. Then, the band F crosses horizontally the three groups G2-G4. At the exit from the machine, rollers R5 guide the strip F to a next working machine, for example for cutting the strip into sheets. It should be noted that the offset machine can also be provided with a drying station S either at the exit of the strip F of the first group Gì to dry the back, or at the exit of the last group G4 to dry the front, or still between groups, for partial drying.

On each side of the strip F and on the frame Ba of each printing unit G1-G4 are provided vertical guides 2 intended to support and guide the arms of a loading-unloading system of the cylinders PP, PB, CC.

Near each group G1-G4 there is a free space for the installation of a carriage 3 on which the three replacement printing cylinders PP ', PB' and CC 'can be placed, that is to say - say for a new job, as shown in fig. 4. In other words, the trolley 3 has the function of transporting the three reserve cylinders PP ', PB', CC 'from a storage location and of placing them perpendicular to the strip and near the cylinders. PP, PB and CC already present. For this purpose, the carriage 3 (fig. 7) consists of a base 31 of length approximately equal to that of the printing cylinders and of a vertical upright 32 connected to one end of the base 31. The base 31 is equipped with four pivotable wheels 33 to allow autonomous movement of the carriage 3. Grooves 34 for movement of the carriage 3 by pallet truck are also provided in the base 31. The carriage 3 comprises three vertically spaced horizontal supports 35a, 35b, 35c and each intended to carry one of the three cylinders PP, PB and CC. Each horizontal support 35a-35c has at each of its ends a support bar 36 provided with a circular notch 36a open upwards and in which a free end of the central shaft 14 of a cylinder can take place. PP, PB, or CC printing. Towards its top, the carriage 3 is provided with a frame 37 intended to facilitate its manual handling. The vertical arrangement of the horizontal supports 35a-35c is such that the printing tape F can, along a horizontal path, pass between the lower support 35a and the intermediate support 35b and arrive between the two cylinders PB and CC. Likewise, between the lower support 35a and the base 31, a free space is provided for the passage of the strip F in the case, for example, of the group Gì of FIG. 4. Thus, as can be seen from FIG. 7, even as the strip runs, that is to say that the offset machine is in production, downstream of each group G1-G4 can be put in place a carriage 3 by moving the latter perpendicular to the direction of movement of the strip F. It should be noted that in FIG. 7, since it is not necessary to provide a band F passage between the two upper 35c and intermediate 35b supports, the free ends of the latter two are interconnected, for reasons of rigidity, by a cross member vertical 38.

In fig. 5 are shown the second and third printing groups G2, respectively G3 when printing the back of the strip F. It is now described the loading-unloading of the printing cylinders PP, PB and CC of the second group G2, it being understood that that of the other groups Gì, G3 and G4 is identical to it.

In fig. 5, the spare cylinders PP ', PB' and CC 'are therefore arranged in the same order as those PP, PB and CC present on the group G2, each spare cylinder PP'. PB ', CC' to take the place of the corresponding one on the

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group G2, and vice versa. For this purpose, as mentioned above, on each side of the strip F are provided vertical guides 2 fixed on the side walls of the frame Ba of group G2. Along each guide 2, can slide a movable support 25 provided with a horizontal axis around which the first end of an arm 26 can pivot. The vertical displacement of the support 25 is ensured by means of a ball screw 23 whose the upper and lower ends are mounted in free rotation, by means of bearings 22a, respectively 22c, on the frame Ba of group G2. The lower ends of the two ball screws 23 are interconnected by transmission means (not shown) and driven simultaneously by the same motor M1. The ball screw 23 is engaged with a corresponding nut 25a provided in the mobile support 25, so as to move the latter by rotation of the ball screw 23. In this way, a simultaneous and identical displacement and positioning are obtained for the two movable supports 25. The pivoting of each arm 26 around the horizontal axis of the corresponding support 25 is obtained by means of a spline shaft 24 whose upper and lower ends are also mounted in free rotation, by means of the bearings 22a, respectively 22c, on the frame Ba of group G2. Likewise, the lower ends of the two splined shafts 24 are connected together by transmission means (not shown) so as to be able to drive them in rotation, simultaneously and at the same speed, by means of a single motor M2. Inside the movable support 2, known means (not shown) are provided for transforming the rotation of the splined shaft 24 into a tilting movement of the arm 26 around the horizontal axis mentioned above. The free end of each arm 26 is provided with telescopic clamps 26a with control by pneumatic cylinders for opening and closing of clamps.

The purpose of each clamp 26a is to grip the corresponding free end of the central axis of one of the three printing cylinders PP, PB and CC. A fixed auxiliary horizontal cross member 21, directed downstream, is mounted, by a first end, on the frame Ba of group G2 near the upper end of each guide 2, the free end also being provided with a semi-circular notch 21a open at the top.

The unloading-loading operation, i.e. the replacement, for example of the small format PP, PB and CC cylinders present on the group G2 (shown in white in FIGS. 5 and 6) by cylinders PP ', PB' and CC 'large format (shown in black in figs. 5 and 6) located on the carriage 3, is carried out as follows (the description being made for only one side since the other side is the same). The free end of the arm 26 is brought, by displacement of the movable support 25 and tilting of the arm 26, near the central shaft 14 of the PP cylinder, so that its clamp 26a can then be engaged with this shaft 14. Once the shaft 14 of the PP cylinder has been gripped by the clamp 26a, the latter is closed (by the pneumatic cylinders mentioned above)

then, by displacement of the support 25 upwards and also by tilting upwards of the arm 26, the cylinder PP is brought into a position such that its central shaft 14 can bear in the notch 21a of the auxiliary support 21. At this instant, the clamp 26a is released from the central shaft 14 of the PP cylinder to be brought, by displacement downwards of the movable support 25 and tilting of the arm 26, near the central shaft of the new large-format PP cylinder ' carried by the carriage 3. The arm 26 can therefore, at this instant, grasp the cylinder PP 'and put it in its place on the group G2. The continuation of the unloading-loading by means of the arm 26 can be summarized as follows:

- unloading of the cylinder PB by its transfer to the support bar 36 of the upper support 35c of the carriage 3 (see also fig. 7);

- loading or installing the PB 'cylinder on the G2 group;

unloading of the cylinder PB by its transfer onto the support bar 36 of the intermediate support 35b of the carriage 3;

- unloading of the CC cylinder by its transfer to an intermediate waiting position (shown in broken lines in Fig. 5; on this subject, even if these means are not shown, it is easy to see that elements, provided with 'notches similar to those 21a of the fixed auxiliary support 21, can be provided on the frame Ba of group G2 to keep the cylinder CC in its standby position);

- loading or positioning of cylinder CC 'on group G2;

- Transfer of the cylinder CC, from the standby position, on the support bar 36 of the lower support 35a of the carriage 3;

- Transfer of the cylinder PB, from the support bar 36 of the upper support 35c, on the support bar 36 of the intermediate support 35b;

transfer of the cylinder PP, from the fixed auxiliary support 21 of the group G2, onto the support bar 36 of the upper support 35c of the carriage 3.

By a judicious choice of the curve describing in space the path of loading or unloading of cylinders PP, PB, CC, PP ', PB' and CC ', it is possible to minimize the time necessary for an unloading operation -loading. Likewise, the order of the sequences of cylinder displacements is given above only by way of example; thus it is possible to mount the fixed auxiliary support 21 directly on the upper end of the carriage 3 and to start by putting the cylinder CC in the waiting position, then the cylinder CC 'on the group G2, then the cylinder CC on the support bar 36 of the lower support 35a, etc.

The method of mounting the PP, PB and CC cylinders on the group G2 must, of course, be such that each clamp 26a can be engaged with a disengaged part of the central shaft 14 of the PP, PB and CC cylinders; means must even be provided for releasing this central shaft 14 with respect to its rotation bearing mounted on the frame Ba of the group, these means possibly being roughly similar to those already used to date

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to allow a change of format of such cylinders. In addition, the fact that the cylinders PP and CC are mounted in group G2 on tilting levers 8, respectively 8 ', also makes it possible to keep them sufficiently distant from the fixed cylinder PB (even in the case of a large format ) to make unloading-loading easier.

It is clear that all the successive unloading-loading operations are fully electronically controlled by a pre-programmed control of the two motors Mi and M2, and that each movement is monitored and released in order to release the next one, thus guaranteeing safety.

From fig. 6 it also appears that it is not necessary to keep the offset machine stopped until all the successive phases of unloading-loading have been completed. In the case of reverse printing, once the three cylinders PP ', PB' and CC 'in new format are on the group, the latter can start to rotate.

It is also clear that partial sequences will be provided, approximately 10 in all, such as exchange of the cylinder PP only, exchange of the cylinder PB only, exchange of the cylinders PP and PB, etc.

These sequences will be chosen automatically by checking the presence of the elements when the carriage has been inserted. This control will be done by read heads, proximity switches or similar means.

Figs. 8 to 10 show an embodiment of the tilting arm 26 and its control means. Here too, only one side will be described, it being understood that the other side is identical to it.

The mobile support 25 is mounted movable vertically along and outside a right-angled corner of the frame Ba of group G2. For this purpose, the mobile support 25, seen from above, has the shape of a block at a right angle matching, but without coming into contact, the corner of the frame Ba. The movable support 25 is provided with a guide groove 51 engaged with a corresponding vertical rail 50 fixed, using screws 52, on the face downstream of the frame Ba. The vertical movement of the support 25 is therefore ensured, as mentioned above, using the ball screw 23 engaged with the corresponding nut 25a (see fig. 10). One end of the arm 26 is fixed on a horizontal axis 80 oriented perpendicularly: to the lateral face of the frame Ba and mounted in rotation, by means of bearings 81, on the mobile support 25. The arm 26, the thickness of which must be reduced at a minimum so that it can be easily introduced into the narrow space located between the end of the cylinder PP, PB or CC and the rocket 100 which supports it in group G2, consists of a first and second plate 61, respectively 62, identical and kept parallel and at a distance from each other by means of a third intermediate plate 60. The common fixing of the three plates 60-62, so as to form a solid assembly in the form of arms 26 , can be achieved by any known means, for example by welding. Locking in rotation of the arm 26 on the axis 80 is obtained using a known system with cone and screw 84

compression which allow frictional coupling.

The intermediate plate 60 is shorter than the two other plates 61, 62 so as to leave between each free end of the latter a free space which can be occupied by two upper and lower movable clamps 26a. The two clamps 26a, which have an exactly identical construction method but symmetrical with one another (see fig. 9), also have an exactly simultaneous operation, even if, in fig. 9, the lower clamp 26a, to facilitate understanding, is shown with its end 60a emerging from the free end of the two plates 61, 62, that is to say of the arm 26, and in engagement, at by means of a semicircular notch 60g open upwards, with the central shaft 14 of one of the cylinders. Each clamp 26a is in the form of a plate of thickness slightly less than that of the intermediate plate 60 so as to be able to slide freely between the two other plates 61, 62. Each clamp 26a therefore consists of the front part 60a with a notch 60g, a rear part 60c and a central part 60e. On the central part 60e are fixed two guide studs 60f, 60h intended to come into engagement with corresponding grooves 61a, 62a, respectively 61c, 62c, of the two plates 61, 62. The shape and the arrangement of the clamp 26a, grooves 61a, 62a and 61c, 62c and studs 60f and 60h are such that when the clamp 26a is moved, by means of a jack Vi, the outlet rod of which is engaged with the rear part 60c of the clamp 26a, towards the front, the notch 60g comes into engagement with the lower (or upper) half of the shaft 14. It should be noted that the arm 26 is so designed that its free end, that is to say that of the two plates 61, 62, comes in the immediate vicinity of the shaft 14 without however being able, whatever the state of its tilting, to come into contact with this shaft 14. Once the notch 60g is engaged with the shaft 14 , a movable locking stud 90, closable by a spring 91 and openable by a pneumatic cylinder V2 mounted on the first plate 61, is engaged with a corresponding orifice 60m of the clamp 26a. At this instant, in the case, for example, where it is unloading, the rocket 100, engaged in the printing unit G2 with the end of the shaft 14, is axially displaced so as to release the latter relative to group G2 and thus allow the weight of the cylinder PP, PB or CC to rest directly on the arm 26.

In order for the arm 26 to be able to execute an unlimited rotation, the supply of pneumatic fluid to the jacks Vi comprises a ring with rotating sealing joints 70 concentric with the axis 80. The fixed ring 70 is pierced with numerous orifices 71 connected, on the one hand, to a pneumatic fluid supply conduit Ci and, on the other hand, to conduits 64 drilled inside the first plate (rotating) 61. The conduits 64, which emerge on a free edge of the plate 61, are then connected by appropriate conduits C2 to the four pneumatic cylinders Vi, V2. The crown 70 is mounted on a cover 74 concentric with the axis 80 and fixed

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to the mobile support 25 by screws 75. As can be seen in FIG. 8, the cover 74 also has the function, in association with successively a circlip 86, a first bearing 81, a washer 87, a toothed crown 88 (described below), a crown-stop 82, a second bearing 81 (mounted in the cover 74) to ensure the axial fixing of the axis 80 inside the movable support 25. The crown 70 is pressed against the arm 61 only when the latter is stopped, because it is there only that cylinders must be actuated. When the arm turns, all pressures are cut, which prevents wear on the seals of crown 70.

The means for driving the axis 80 in rotation comprise a first pinion 10 (see FIG. 10) fixed on the nut 25c and in engagement with a second pinion 11 mounted locked in rotation on an axis 12. On this rotary axis 12, the ends of which are mounted in rotation by means of bearings 13a, 13b inside the movable support 25, an endless screw 14 is fixed, engaged with the corresponding toothed crown 88 mounted linked in rotation, using of pins 82a engaged with the stop 82, on the axis 80.

It is obvious that the embodiment of the arm 26 described above is given only by way of example, it being understood that many variants are possible. Thus, the arm 26 may consist of a single plate in which is made a free space for the clamps 26a. In the case where it is not intended to make the arm 26 complete a revolution, the pneumatic supply of the jacks can be made directly by flexible hoses, that is to say without the use of the rotating crown with watertight joints. The clamps 26a can be controlled electrically, etc.

Note that the arrangement shown by way of example has the advantage of being self-locking in the event of a pneumatic pressure rupture or in the event of an electrical failure. In addition, it was created as compact as possible.

Figs. 11 and 11A to 11D show an exemplary embodiment of the rocket 100 supporting each cylinder PP, PB, CC in a group G1-G4. The rocket 100 consists of a crown 101 provided with three pairs of two connecting rods 102, 103 hinged together, three pairs being distributed angularly around the axis of the shaft 14 of a cylinder PP, PB, CC . The assembly constituted by the crown 100 and the connecting rods 102, 103 can be moved between a first position (shown in the upper half of FIG. 11) in which a hook-shaped part 102a of a connecting rod 102 is engaged with a corresponding groove 14a of the shaft 14, and a second position (shown in the lower half of FIG. 11) in which the connecting rods 102, 103 are sufficiently distant from the shaft 14 to allow removal of the cylinder PP , PB, CC as described above. To achieve the displacement of the connecting rods 102, 103, one 103 is articulated to the crown 100, the other 102 to a cylinder 400 rotatably mounted in the frame Ba of the machine. The axis of the cylinder 400 is coincident with that of the shaft 14. Inside the cylinder 14 is mounted a shaft 401 displaceable by means of a jack (located on the side of the non-visible end of the cylinder 400 ) between the two positions shown in fig. 11, that is to say between a first position in which a conical end 401a emerges from the cylinder 400 and is engaged with a corresponding conical part 14a of the shaft 14 and a second position in which this same conical end 401a is completely retracted inside the cylinder 400. The crown 101, mounted concentric and sliding with respect to the cylinder 400, is fixed, by screws 105, to three radial studs 402 angularly distributed and engaged with the inner shaft 401 of so as to simultaneously move this shaft 401 and the crown 100. FIGS. 11A to 11D show the different positions of the connecting rods 102, 103 as a function of that of the crown 101. In summary, it is possible to say that the conical parts 401a, 14a establish a radial connection, and the hooks 102a and groove 14a a connection axial of the shaft 14 relative to the cylinder 400.

Claims (1)

Claims 1. Offset printing machine, with variable format, on tape, with at least one printing unit (G1-G4) each comprising: - a fixed lower frame (Ba) on which can be mounted plate (PP), blanket (PB) and pressure (CC) printing cylinders whose diameter varies with that of the printing format, three cylinders (PP, PB, CC) being arranged in an essentially vertical line, and in the order in which the plate cylinder (PP) is the highest; - a mobile upper part or cassette (CE) comprising an inking unit (E) with inkwell (Ei) and bubbling rollers (È2), distributors (E3) and touchers (E4), and a wetting unit (M) with a tank (M1) and bubbler rollers (M2), distributors (M3) and touchers (M4); and - a unit for washing the blanket cylinder (PB) mounted on said frame (Ba), characterized in that: - the cassette (CE) is displaceable between a first lower position in which the touch rollers (E4, M4) can come into contact with the plate cylinder (PP) in the case of said minimum format, and a second upper position in which the touch rollers (E4, M4) are sufficiently distant from the plate cylinder (PP) to allow, in the case of said maximum format, unloading-loading of the printing cylinders (PP, PB, CC); and - mobile means (26a), mounted on each side of the frame (Ba), are intended to come into engagement with each end of the central shaft of each cylinder (PP, PB, CC) present on the group (G1-G4 ) with a view to unloading them on support bars (36) located near the downstream side of the corresponding group (G1-G4), the mobile means (26a) also being provided for, similarly to unloading, engaging each end of the central shaft of the cylinders (PP ', PB', CC ') again for5 10 15 20 25 30 35 40 45 50 55 60 65 6 11 CH 682 896 A5 12 mast mounted on support bars (36) also located close downstream of said group (G1-G4) to load them on the latter, the control and movement of the mobile means (26a) being entirely managed by microprocessor. 2. Machine according to claim 1, characterized in that: - Said movable means are constituted by telescopic clamps (26a) with opening and closing situated at the free end of at least one tilting arm (26) the other end of which is pivotally mounted, along a horizontal axis, on a support movable (25) essentially vertically along guides (2) provided on the frame (Ba); - Said support bars (36), located near the group (G1-G4), are mounted on a carriage (3) with independent movement, so that, by a movement of the carriage (3) essentially perpendicular to the direction strip (F), the new format cylinders (PP ', PB' and CC ') can be brought close to and around the location of the cylinders (PP, PB, CC) present in the group (G1-G4) so that, by appropriate tilting and displacement of the arm (26), respectively of the movable support (25), the grippers (26a) can unload the cylinders (PP, PB, CC) present on the group (Gi-G4) and a loading of cylinders (PP ', PB', CC ') in new format. 3. Machine according to claim 2, characterized in that: - The vertical displacement of each mobile support (25) is obtained by means of a vertical ball screw (23) engaged with a nut (25a) corresponding to the mobile support (25), the rotation drive of the two screws balls (23), located on each side of the frame (Ba), being produced by a single motor (Ni) to obtain a simultaneous and identical displacement and positioning of the two corresponding mobile supports (25); - the tilting of each arm (26) is obtained by means of a vertical grooved shaft (24) engaged with corresponding means (25c) provided on the mobile support (25) to transform the movement into rotation of the shaft splined (24) in a tilting of the arm (26) around said horizontal axis, the rotation drive of the two splined shafts (24) located on each side of the frame (Ba) being produced by a single motor (N2) to obtain a simultaneous and identical tilting and positioning of the two corresponding arms (26). 4. Machine according to claim 2, characterized in that the carriage (3) comprises: - A horizontal base (31) of length approximately equal to that of the printing cylinders (PP, PB, CC) provided with swivel wheels (33) and / or grooves (34) for movement by pallet truck; - a vertical upright (32) fixed to one end of the base (31); - at least three horizontal supports (35a, 35b, 35c) vertically spaced, parallel to the base (31), fixed by one end to the vertical upright (32) and provided, at each end, with a support bar ( 36) with a notch (36a) open upwards in which the end can bear blanket cylinder of the printing cylinder (PP, PB, CC) in such a way that, by moving the carriage (3) perpendicular to the direction of travel of the strip (F), the blanket cylinders (PB ') and plate holder (PP') and the pressure cylinder (CC ') occupy, at said proximity of the group (Gì, G2), a position located above, respectively below, the band (F ). 5. Machine according to claim 4, characterized in that: - only one mobile means (26a) is provided on each side of the frame (Ba); - auxiliary supports (21, 21a or 21 ', 21'a) are provided either on the frame (Ba) of the group, or on the carriage (3); - Said displacement of the movable means (26a) being carried out so that it can perform the successive unloading-loading of the printing cylinders (PP, PB, CC, PP ', PB', CC ') using, when necessary , the auxiliary supports (21, 21a or 21 ', 21'a) as an intermediate waiting station for one of said printing cylinders. 6. Machine according to claim 4, characterized in that the carriage (3) is also arranged to allow a passage of tape between the base (31) and the pressure cylinder (CC) in the case of double-sided printing . 7. Machine according to claim 5, characterized in that an upper auxiliary support (21, 21a) is situated above, and the other lower support (21 ', 21'a) below the printing cylinders, the plate cylinder (PP, or PP ') and the pressure cylinder (CC, CC') being placed, during the unloading-loading operation, on standby on the upper auxiliary support (21, 21a), respectively lower (21 ', 21'a), when no space is available on the carriage (3) or, respectively, on the group (G1-G4). 8. Machine according to claim 5, characterized in that the blanket cylinder (PB) is fixed and that the plate cylinders (PP) and pressure (CC) are mounted, at each of their ends, on the first end of a rocking lever (8, respectively 8 '), the other end of which is mounted in rotation along a horizontal axis (81, respectively 81') fixed on the frame (Ba). 9. Machine according to claim 2, in which the printing units (G1-G4) are simultaneous unloading-loading. 10. Machine according to claim 2, characterized in that the arm (26) is in the form of at least one plate (60, 61, 62) one end of which is pivotally mounted around the axis (80) and the free end of which is provided with two clamps (26a) capable of occupying a first position in which, when the arm (26) tilts, it cannot come into contact with the central shaft (14) of the printing cylinders (PP, PB, CC), and a second position in which they can engage with this same tree (14). 11. Machine according to claim 10, characterized in that the two clamps (26a) are identical, but symmetrical with respect to each other, each being provided with guide means (60f, 60h), engaged with corresponding means (61a, 62a, respectively 61c, 62c) of the arm (26), 5 10 15 20 25 30 35 40 45 50 55 60 65 7 CH 682 896 A5 which ensure, during the transition from said first to said second position, the guiding, opening and closing of the two clamps (26a), locking means (90) in position of the clamps (26a) relative to the arm (26 ), when they are engaged with the central shaft (14), being provided. 12. Machine according to claim 11, characterized in that the movement and locking of the clamps (26a) are carried out by pneumatic cylinders (Vi, respectively V2). 13. Machine according to claim 12, characterized in that a rotary joint (70) with concentric tightness to the pivot axis (80), ensures the distribution of the pneumatic fluid between conduits (71) provided in the rotary joint ( 70) fixed and conduits (64) provided in the pivoting arm (26) and connected to the pneumatic cylinders (Vi, V2). 14. Machine according to claim 3, characterized in that the means for transforming the rotation of the spline shaft (24) into a rotational movement of the axis (80) comprise a first toothed pinion (10) mounted on the 'nut (25c) and engaged with a second toothed pinion (11) mounted linked in rotation with a rotary axis (12) provided with a worm gear (44) engaged with a corresponding crown gear (88) linked in rotation with the axis (80). 15. Machine according to claim 10, provided with retractable means intended to support in rotation each end of a central shaft (14) of printing cylinder (PP, PB, CC), characterized in that said retractable means comprise: - a rotary cylinder (400) mounts on the frame (Ba) of the machine; - a movable shaft (401), inside the cylinder (400), between a first position in which one of its ends (401a) emerges from the cylinder (400) and in radial engagement with a corresponding part (14a) of the shaft (14), and a second position in which, by axial displacement, said end (401a) is released from the central shaft (14); and - movable means (102a), in relation to the lower shaft (401) between a first position in which they are in axial engagement with corresponding means (14a) provided on the central shaft (14), and a second position in which they are released from this same tree (14). 5 10 15 20 25 30 35 40 45 50 55 60 65 8